In recent years, advances in miniaturization have generated a great variety of personal electronic devices. Indeed, many people have come to depend on cellular telephones, electronic address books, personal digital assistants (PDA's) and pagers for their day-to-day professional lives. Likewise, consumer electronics such as personal stereos and hand-held video games are common recreational devices.
A feature common to all these personal electronics is the need for some type of energy storage to supply power. Particularly in off-grid areas or regions with irregular power supply, batteries remain as the predominant form of energy. Users need to carry multiple batteries to power their devices and also need to be able to provide a whole range of voltage and current ratings to meet the power requirements of different appliances. Even in areas with constant grid power, high drain devices such as cellular telephones, often require the user to carry multiple batteries and perhaps a charging station for even relatively short trips. The user must constantly track the remaining battery capacity for each device to ensure that the charge will hold for a desired length of time.
Alternatively, the user must carry spare batteries. Since each electronic device typically has its own requirements and form factors, the user might be forced to carry several different spare batteries to power the various devices. It is also quite desirable to provide these personal electronic devices with rechargeable batteries, both for their relative economy and to minimize environmental impact. However, such recharging systems are rarely compatible. One device's charger often will not recharge another's battery, nor will that battery be usable with a different device.
In the prior art the devices are mentioned in U.S. Pat. Nos. 5,783,327, 6,027,828. These devices stack batteries for discharging and require special connections and switches to create different voltages. The single use batteries are discarded after the charge is depleted. However, some batteries are designed to be rechargeable. Rechargeable batteries typically require some form of battery charging system. Typical battery charging systems transfer power from a power source, such as an AC wall plug, into the battery. The recharging process typically includes processing and conditioning voltages and currents from the power source so that the voltages and currents supplied to the battery meet the particular battery's charging specifications. For example, if the voltages or currents supplied to the battery are too large, the battery can be damaged or even explode. On the other hand, if the voltages or currents supplied to the battery are too small, the charging process can be very inefficient or altogether ineffective. Inefficient use of the battery's charging specification can lead to very long charging times, for example. Additionally, if the charging process is not carried out efficiently, the battery's cell capacity (i.e., the amount of energy the battery can hold) may not be optimized. Moreover, inefficient charging can impact the battery's useful lifetime (i.e., number of charge/discharge cycles available from a particular battery). Furthermore, inefficient charging can result from the battery's characteristics changing over time. These problems are compounded by the fact that battery characteristics, including a battery's specified voltages and recharge currents, can be different from battery to battery.
Existing battery chargers are typically static systems. The charger is configured to receive power from a particular source and provide voltages and currents to a particular battery based on the battery's charge specification. However, the inflexibility of existing chargers results in many of the inefficiencies and problems described above. It would be very advantageous to have battery charging systems that were more flexible than existing systems or even adaptable to particular batteries or the changing battery charging environment. Thus, there is a need for improved battery charger systems and methods that improve the efficiency of the battery charging process.
Accordingly, there has been a need for a system to integrate the power supplies of multiple personal electronic devices. There has also been a need for a power management system that knows, what it is being charged from, what it is charging and how much power it is to deliver.
In places that are currently off the grid or receive an unreliable supply of power, there is a lack of choice to purchase a multipurpose power source that can be used to power a wide variety of electronics. Largely, people have access to singular appliances such as solar powered LED lanterns, solar fans, heaters etc. To buy each new appliance, the user must purchase the entire set of generator, storage device and the end appliance. These components are usually integrated into one device and the user can use them only for a particular application, for example lighting. Thus, there is an urgent need of a power management system that can be used to power a variety of appliances and that can be connected to more than one end appliance simultaneously. There is also a need of a power management system that be charged by all available renewable sources of energy or, thus making optimum use of the available resources.
In areas described above, the current solutions like solar lanterns are extremely expensive for the end user. Since typical family incomes in these regions are around $40-$150/month, a single solar lantern usually costs upwards of 50% of the monthly household income. Other solutions like kerosene or diesel powered microgrids are extremely harmful to the environment and provide mostly lighting for very few hours/day because of their high operational costs. Thus, there is a need for a power management system that can not only provide high utility by powering a whole range of appliances like lights, fans, radios, cell phones, TVs, and other commonly found household appliances, but it also needs to be purchased in small cash amounts over a period of time since income levels in these areas are extremely low. Thus, to ensure regular payments the power source needs to be smart enough to deactivate itself after expiration of the installment/payment period. Also, it should be able to get activated for a fixed period of time based on how many installments have been paid by a user. This allows users to adopt a payment scheme suited to their varying income levels thus making the device extremely affordable.
The power sources as disclosed under prior art batteries do not allow different kinds of input generators to charge the unit. Though stacking of the sources are disclosed in the prior art but they are not facilitated for charging and/or output purposes simultaneously. The present disclosure provides a solution overcoming the prior art problems by proposing a stack, wherein, without any moving part, two modules can be stacked together by simply placing one on top of the other. The inputs and outputs get connected automatically to enable simultaneous multi-cell charging and high power dissipation. When stacked, there is more than one module producing the output and thus the total output power increases linearly with the number of units stacked. This further cleans the output voltage since the errors due to passive components get averaged. Thus, high power appliances can be operated with even better input power characteristics.